Research On Foot Force Adaptive Motion Control Of Hexapod Robot Based On Active Impedance Method

With the rapid development of robot control technology,many novel control methods have emerged.For the hexapod robot,its fuselage structure is redundant,and there are many leg joints,which need to move in a special trajectory,which puts forward higher requirements for the control of the robot.When only the joint position is generally controlled,the foot end of the robot cannot sense the ground environment in a complex terrain environment,and the foot force does not match the contact terrain,causing the robot to lose stability or even overturn.To solve this problem,this paper will design a hexapod robot control system to realize the self-adaptive control method according to the terrain environment.The main work is as follows:(1)Using the arthropod spider as the biological prototype,design the body and leg structure of the hexapod robot with bionic ideas.The torso of the robot is designed in a hexagonal structure,each leg is distributed on six vertices,and the leg unit is composed of four degrees of freedom.Based on the body and leg structure,the forward and inverse kinematics of the leg is analyzed,and the trajectory space of the foot end is analyzed by means of random number method.(2)Design the inner loop based on position control.A rhythm control module based on the Central Pattern Generator(CPG)signal network is designed to control the movement speed,gait cycle,gait form and duty cycle of the robot when it is moving.At the same time,the body steering and translation motion forms based on circles and straight lines are also designed,so that the hexapod robot can realize multi-directional flexible motion by changing its motion control parameters.On the basis of establishing the movement direction control of the fuselage,this paper adopts the Bezier curve as the swing phase to ensure the smooth trajectory of the foot and the flexible and continuous switching.(3)In view of the inability of the position control mode to control the robot to stand stably in different terrain environments,the outer loop foot force adaptive feedback control design is introduced.In this paper,based on the active impedance method of indirect force control,an outer loop feedback control method of environmental parameter adaptation is introduced.Based on the established leg impedance model,this method corrects the environmental parameters with a real-time estimation algorithm,indirectly changes the position of the foot to adapt to the terrain environment,and realizes the adaptive control of the foot force.In view of the instability of the fuselage attitude and fuselage height during robot foot force control,the PD(Proportional-Derivative)feedback control method for fuselage height and attitude control is introduced to correct the expected foot force of the robot support phase in real time to ensure the stability of the fuselage when the operating environment changes.(4)Carry out multiple sets of verification experiments according to theoretical analysis.The results of progressive comparison experiments prove that the control algorithm in this paper can control the robot’s flexible steering movement,quickly estimate the environmental parameters,and realize the stable following of the expected foot force in different terrain environments.And after the attitude and height control of the fuselage,the pitch angle and roll angle of the robot fuselage only fluctuate within a small range,and the overall movement is stable.